U.S. patent number 7,250,542 [Application Number 10/793,028] was granted by the patent office on 2007-07-31 for paraffin alkylation.
This patent grant is currently assigned to Catalytic Distillation Technologies. Invention is credited to John R. Adams, Abraham P. Gelbein, Mitchell E. Loescher, Lawrence A. Smith, Jr..
United States Patent |
7,250,542 |
Smith, Jr. , et al. |
July 31, 2007 |
Paraffin alkylation
Abstract
A process for the alkylation of alkane with olefin or olefin
precursor such as an oligomer of tertiary olefin comprising
contacting a liquid system comprising acid catalyst, isoparaffin
and olefin in concurrent downflow into contact in a reaction zone
with a disperser mesh under conditions of temperature and pressure
to react said isoparaffin and said olefin to produce an alkylate
product is disclosed. Preferably, the liquid system is maintained
at about its boiling point in the reaction zone. Unexpectedly, the
olefin oligomers have been found to function as olefin precursors
and not as olefins in the reaction. Thus, for example, a cold acid
alkylation using an oligomer of isobutene (principally dimer and
trimer) with isobutane produces isooctane with the isobutane
reacting with the constituent isobutene units of the oligomers on a
molar basis. The product isooctane is essentially the same as that
produced in the conventional cold acid process.
Inventors: |
Smith, Jr.; Lawrence A.
(Houston, TX), Loescher; Mitchell E. (Houston, TX),
Adams; John R. (Houston, TX), Gelbein; Abraham P. (Falls
Church, VA) |
Assignee: |
Catalytic Distillation
Technologies (Pasadena, TX)
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Family
ID: |
31886603 |
Appl.
No.: |
10/793,028 |
Filed: |
March 4, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040171901 A1 |
Sep 2, 2004 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10219877 |
Aug 15, 2002 |
6858770 |
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60334560 |
Nov 30, 2001 |
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60323227 |
Sep 19, 2001 |
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60313987 |
Aug 21, 2001 |
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Current U.S.
Class: |
585/332; 585/720;
585/723; 585/730; 585/721; 585/709; 585/520 |
Current CPC
Class: |
C10G
29/205 (20130101); C07C 2/62 (20130101); C07C
11/02 (20130101); C10G 2300/1088 (20130101); C10G
2300/1081 (20130101); C07C 2527/054 (20130101) |
Current International
Class: |
C07C
6/00 (20060101); C07C 2/58 (20060101); C07C
2/62 (20060101) |
Field of
Search: |
;585/332,720,723,730,520,709,721 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wood; Elizabeth D.
Attorney, Agent or Firm: Osha.cndot.Liang LLP
Parent Case Text
This application is a division of U.S. Ser. No. 10/219,877, filed
on Aug. 15, 2002, and now U.S. Pat. No. 6,858,770 which claims the
benefit of provisional application 60/313,987 filed Aug. 21, 2001,
provisional application 60/323,227 filed Sep. 19, 2001 and
provisional application 60/334,560 filed Nov. 30, 2001.
Claims
The invention claimed is:
1. An integrated process for the production of alkylate comprising
contacting a stream comprising normal and tertiary olefins with an
acid cation resin catalyst under oligomerization conditions to
preferentially react a portion of the tertiary olefins with
themselves to form oligomers and feeding said oligomers and
isoalkane to an alkylation zone under alkylation conditions in the
presence of an acid alkylation catalyst in concurrent downflow
under conditions of temperature and pressure to maintain said
liquid system at about its boiling point through a reaction zone
packed with disperser contacting internals comprising liquid-liquid
coalescers; to dissociate said oligomer into its constituent
olefins and to react said constituent olefins with said isoalkane
to produce an alkylation product comprising the alkylate of said
tertiary olefins and said isoalkane.
2. The process according to claim 1 wherein said stream comprises a
light naphtha C.sub.4-C.sub.5 cut, a C.sub.4 cut or a C.sub.5
cut.
3. The process according to claim 2 wherein said stream comprises
isobutene.
4. The process according to claim 2 wherein said stream comprises
isoamylenes.
5. The process according to claim 2 wherein said isoalkane
comprises isobutane, isopentane or mixtures thereof.
6. The process according to claim 3 wherein said isoalkane
comprises isobutane, isopentane or mixtures thereof.
7. The process according to claim 4 wherein said isoalkane
comprises isobutane, isopentane or mixtures thereof.
8. The process according to claim 2 wherein the acid alkylation
catalyst comprises sulfuric acid.
9. The process according to claim 8 wherein said alkylation is
carried out at a temperature in the range of range from about
0.degree. F. to about 200.degree. F. and a pressure in the range of
from about 0.5 ATM to about 50 ATM.
10. The process according to claim 2 wherein said acid alkylation
catalyst comprises HF.
11. The process according to claim 2 wherein said tertiary olefin
comprises isobutene, isopentene or mixtures thereof, said isoalkane
comprises isobutane, isopentane or mixtures thereof, said acid
alkylation is sulfuric acid and said alkylation is carried out at a
temperature in the range of range from about 0.degree. F. to about
200.degree. F. and a pressure in the range of from about 0.5 ATM to
about 50 ATM.
12. The process according to claim 11 wherein said alkylation
product comprises isooctane.
13. A process for the production of alkylate comprising the steps
of reacting olefins with themselves to form oligomers and
contacting the oligomerization product with an alkane in the
presence of an alkylation catalyst in concurrent downflow under
conditions of temperature and pressure to maintain said liquid
system at about its boiling point through a reaction zone packed
with disperser contacting internals comprising liquid-liquid
coalescers to dissociate said oligomerization product into its
constituent olefins and to react with said alkane to produce
alkylate.
14. The process according to claim 13 wherein said alkylation
catalyst is sulfuric acid.
15. The process according to claim 13 wherein said alkylation
catalyst is hydrofluoric acid.
16. The process according to claim 13 wherein the oligomerization
product is in the vapor phase, the alkane is in the liquid phase
and the alkylation catalyst is in the liquid phase.
17. The process according to claim 13 wherein the oligomerization
product is in the liquid phase, the alkane is in the vapor phase
and the alkylation catalyst is in the liquid phase.
18. The process according to claim 13 wherein the alkylation
catalyst is in the solid phase.
19. The process according to claim 13 wherein the alkylation
catalyst is in the vapor phase.
20. The process according to claim 13 wherein said olefins comprise
C.sub.2 to C.sub.16 olefins.
21. The process according to claim 20 wherein said olefins comprise
C.sub.2 to C.sub.16 tertiary olefins.
22. The process according to claim 13 wherein said alkanes comprise
iso alkanes.
23. A process for the production of alkylate comprising the steps
of reacting C2 to C16 tertiary olefins with themselves to form
oligomers and contacting the oligomerization product with isoalkane
in the presence of an acid alkylation catalyst in concurrent
downflow under conditions of temperature and pressure to maintain
said liquid system at about its boiling point through a reaction
zone packed with disperser contacting internals comprising
liquid-liquid coalescers to dissociate said oligomerization product
into its constituent olefins which react with said isoalkane to
form alkylate.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the alkylation of paraffinic
hydrocarbon feed stocks. The present invention provides both an
improvement in the operating conditions and the feed stock for acid
paraffin alkylations.
2. Related Information
The common objective of most alkylation processes is to bring
isoalkanes (or aromatics) and light olefins into intimate contact
with an acid catalyst to produce an alkylation product. In the
petroleum refining industry, acid catalyzed alkylation of aliphatic
hydrocarbons with olefinic hydrocarbons is a well known process.
Alkylation is the reaction of a paraffin, usually isoparaffins,
with an olefin in the presence of a strong acid which produces
paraffins, e.g., of higher octane number than the starting
materials and which boil in range of gasolines. In petroleum
refining the reaction is generally the reaction of a C.sub.3 to
C.sub.5 olefin with isobutane.
In refining alkylations, hydrofluoric or sulfuric acid catalysts
are most widely used under low temperature conditions. Low
temperature or cold acid processes are favored because side
reactions are minimized. In the traditional process the reaction is
carried out in a reactor where the hydrocarbon reactants are
dispersed into a continuous acid phase.
Although this process has not been environmentally friendly and is
hazardous to operate, no other process has been as efficient and it
continues to be the major method of alkylation for octane
enhancement throughout the world. In view of the fact that the cold
acid process will continue to be the process of choice, various
proposals have been made to improve and enhance the reaction and,
to some extent, moderate the undesirable effects.
U.S. Pat. No. 5,220,095 disclosed the use of particulate polar
contact material and fluorinated sulfuric acid for the alkylation.
U.S. Pat. Nos. 5,420,093 and 5,444,175 sought to combine the
particulate contact material and the catalyst by impregnating a
mineral or organic support particulate with sulfuric acid.
Various static systems have been proposed for contacting
liquid/liquid reactants, for example, U.S. Pat. Nos. 3,496,996;
3,839,487; 2,091,917; and 2,472,578. However, the most widely used
method of mixing catalyst and reactants is the use of various
arrangements of blades, paddles, impellers and the like that
vigorously agitate and blend the components together, for example,
see U.S. Pat. Nos. 3,759,318; 4,075,258; and 5,785,933.
The present application presents a significant advance in the
technology relating to alkylation and, in particular, to petroleum
refining paraffin alkylation by providing both an effective method
for the alkylation, novel olefinic feed and an apparatus for
obtaining a high degree of contact between the liquid catalyst and
the fluid reactants without mechanical agitation thereby
eliminating shaft seals, reducing costs and improving acid product
separation.
SUMMARY OF THE INVENTION
There are two aspects to the present invention. The first aspect is
a process for the alkylation of paraffin, preferably isoparaffin
with olefin or olefin precursor comprising contacting a fluid
system comprising acid catalyst, alkane and olefin in concurrent
flow, preferably downflow into contact in a reaction zone with
internal packing, such as a disperser (as hereinafter described)
under conditions of temperature and pressure to react said
isoparaffin and said olefin to produce an alkylate product.
Preferably, the fluid system comprises a liquid and is maintained
at about its boiling point in the reaction zone.
The second aspect of the present invention focuses on the olefin in
the alkylation which is characteristic of an olefin precursor. The
olefin precursor is an oligomer of one or more tertiary olefins
such as the dimer, trimer, etc. of isobutene or a material which
corresponds to said oligomer. In a particular embodiment, the
present alkylation employs oligomers of tertiary olefins as the
olefin component of the alkylation with isoalkanes.
It has been surprisingly discovered that olefin reactants that
correspond to oligomers of olefins (for example, the longer chain
oligomers of olefins made by polymerizing shorter chain olefins)
when reacted in an acid alkylation with an isoalkane react on a
molar basis with the constituent olefins of the oligomer, rather
through the oligomers, per se, to produce alkylate product of the
constituent olefin(s) and the isoalkane and not the alkylate of the
oligomer per se as expected. The reaction may be carried out in an
apparatus comprising a vertical reactor containing a disperser or
other suitable packing in the reaction zone which may comprise the
entire column or a portion thereof.
BRIEF DESCRIPTION OF THE DRAWING
The FIGURE is a schematic representation of the first aspect of the
present apparatus in which the present alkylation process may be
carried out.
DETAILED DESCRIPTION OF THE INVENTION
The reaction of oligomer of tertiary olefins with isoalkanes is on
a molar basis with the constituent tertiary olefins of the oligomer
rather than the oligomers. The alkylate product corresponds to the
reaction of the tertiary olefin and isoalkanes.
For the purpose of illustration and not a limitation of the
process, it is believed that instead of the expected reaction
between the oligomer and the isoalkane, the oligomer is cracked
into its olefin components which react with the isoalkane on a
molar basis: 1) diisobutene+2 isobutane.fwdarw.2 isooctane
(2,2,4-trimethyl pentane) 2) triisobutene+3 isobutane.fwdarw.3
isooctane (2,2,4-trimethyl pentane)
The conventional view had been that the product of 1) would be a
C.sub.12 alkane and the product of 2) would be a C.sub.16 alkane
whereas the product of reactions 1) and 2) is the same and is
indistinguishable from a conventional cold acid alkylation product
of the reaction: 3) 2 butene-2+2 isobutane.fwdarw.2 isooctane 4) 3
butene-2+3 isobutane.fwdarw.3 isooctane
The great advantage of the present invention is that although acid
alkylations are extremely exothermic and require substantial
refrigeration to maintain the reaction temperature in optimum range
to prevent side reactions, the present reaction of the oligomers
with the isoalkane to produce the alkylate in the same yields
required less refrigeration making the process less expensive for
the same yield of useful product.
One particular method of producing oligomer is that carried out in
a catalytic distillation, for example, units formerly used to
produce MTBE can readily be converted to producing oligomer merely
by changing the feed to the reactor since the same catalyst serves
both reactions.
Preferably, the oligomer comprises C.sub.8 to C.sub.16 olefins
corresponding to oligomer prepared from C.sub.3 to C.sub.5 olefin.
In a preferred embodiment the oligomer has 6 to 16 carbon atoms and
corresponds to oligomers which are prepared from C.sub.4 to C.sub.5
olefins. The process may be carried out wherein the oligomerization
product is in the vapor phase, the alkane is in the liquid phase
and the alkylation catalyst is in the liquid phase or wherein the
oligomerization product is in the liquid phase, the alkane is in
the vapor phase and the alkylation catalyst is in the liquid
phase.
The widest use of the paraffin alkylation is for the preparation of
a C.sub.8 gasoline component. The feed to this process is usually
normal butene and tertiary butane contained in a "cold acid"
reaction usually with sulfuric acid or HF. The normal butene
(butene-2, for example) is a component of light naphtha along with
normal butane, isobutane and tertiary butene. The separation of the
normal butene from the isobutene can be effected by fractionation
with difficulty because of their close boiling point. A preferred
way to separate these olefin isomers or those of the C.sub.5
analogs is to react the more reactive tertiary olefin to form a
heavier product which is easily separated from the normal olefins
by fractionation.
Heretofore, the tertiary olefin was reacted with a lower alcohol,
such as methanol or ethanol, to form ethers, such as methyl
tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE),
tertiary amyl methyl ether (TAME) which have been used as gasoline
octane improvers but are being phased out because of health
concerns.
The oligomerization of the tertiary olefin is also a preferred
reaction when carried out on a naphtha stream with the separation
of normal olefin being easily achieved by fractionation from the
heavier (higher boiling) oligomers (mainly dimer and trimer). The
oligomers may be used as gasoline components but there are limits
to the amount of olefin material desirable or allowed in gasoline
and it is frequently necessary to hydrogenate the oligomers for use
in gasoline. The most desirable component for gasoline blending is
C.sub.8, e.g., isoctane (2,2,4 trimethyl pentane).
The oligomer may be cracked back to the original tertiary olefins
and used in cold acid reaction. However, the present invention has
found that it is not necessary to crack the oligomer which may
constitute the olefin feed to cold acid reaction with the alkane or
may be co-fed with mono olefins. As noted above the result is the
same product as the mono olefin alone with the additional benefit
of a less exothermic overall reaction requiring less refrigeration
and, hence, a lower energy cost for the alkylation.
The oligomerization process produces a heat of reaction that does
not require the magnitude of heat removal as in the cold acid
process. In fact, when the oligomerization is carried out in a
catalytic distillation type reaction, the heat of reaction is
removed as boilup, which in this type of reaction is the lower
boiling mono olefins and alkanes which are being separated from the
oligomer. Thus, even though there is heat produced in the
oligomerization it is of no cost to the production of the gasoline
since it is used in the fractionation, and the operating cost of
the alkylation unit is reduced by the use of oligomer to replace
some or all of the conventional short chain olefin.
In a preferred embodiment of the present alkylation process, a
light naphtha stream comprising normal and tertiary olefins is
contacted with an acid resin catalyst under oligomerization
conditions to preferentially react a portion of the tertiary
olefins with themselves to form oligomers, and feeding said
oligomers to an alkylation zone with an isoalkane in the presence
of an acid alkylation catalyst to produce an alkylation product
comprising the alkylate of said tertiary olefin and said
isoalkane.
The oligomerization may be carried out in a partial liquid phase in
the presence of an acid cation resin catalyst either in straight
pass type reaction or in a catalytic distillation reaction where
there is both a vapor and liquid phase and a concurrent
reaction/fractionation. Preferably, the feed is a C.sub.4-C.sub.5,
C.sub.4 or C.sub.5 light naphtha cut. The tertiary olefins may
include isobutene, and isoamylenes and are more reactive than the
normal olefin isomers and are preferentially oligomerized. The
primary oligomer products are dimers and trimers. The isoalkanes
preferably comprise isobutane, isopentane or mixtures thereof.
When a straight pass reactor is used, such as that disclosed in
U.S. Pat. Nos. 4,313,016; 4,540,839; 5,003,124; and 6,335,473, the
entire effluent comprising the oligomer, normal olefins and
isoalkanes may be fed to an acid alkylation reaction. The normal
alkanes are inert under the conditions of the present alkylation.
Under alkylation conditions the isoalkane reacts with the normal
olefin to form alkylate product and with the individual constituent
olefins of the oligomers to form the alkylate product. The
implication of the result of the present process is that the
oligomers are dissociated or in some manner make their constituent
olefins available for reaction with isoalkanes. Thus, the reaction
will produce: 1) isobutene oligomer+isobutane.fwdarw.isooctane; 2)
isobutene oligomer+isopentane.fwdarw.branched C.sub.9 alkanes; 3)
isoamylene oligomer+isobutane.fwdarw.branched C.sub.9 alkanes; 4)
isoamylene oligomer+isopentane.fwdarw.branched C.sub.10
alkanes;
whereas it would have been expected that reaction 1) would produce
at least or mostly C.sub.12 alkanes, reaction 2) would produce at
least or mostly C.sub.13 alkanes, reaction 3) would produce at
least or mostly C.sub.14 alkanes, and reaction 4) would produce at
least or mostly C.sub.15 alkanes.
When a catalytic distillation reaction such as that disclosed in
U.S. Pat. Nos. 4,242,530 or 4,375,576 is employed for the
oligomerization, the oligomer is separated from the lower boiling
normal olefins and alkanes in the reaction product by concurrent
fractionation. The streams, normal olefins and alkanes (overheads)
and oligomers (bottoms), may be united or individually fed to the
alkylation or may be used individually with at least the oligomer
being fed to the alkylation.
The present invention offers an improved contacting apparatus and
process for producing and separating an alkylate product using
sulfuric acid as catalyst. This same or similar device may also be
used with other acids or acid mixtures.
The present process preferably employs a downflow reactor packed
with contacting internals or packing material (which may be inert
or catalytic) through which passes a concurrent multi phase mixture
of sulfuric acid, hydrocarbon solvent and reactants at the boiling
point of the system. The system comprises a hydrocarbon phase and
an acid/hydrocarbon emulsion phase. A significant amount of
sulfuric acid is held up on the packing. Reaction is believed to
take place between the descending hydrocarbon phase and the
sulfuric acid dispersed on the packing. Olefin continuously
dissolves into the acid phase and alkylate product is continuously
extracted into the hydrocarbon phase. Adjusting the pressure and
hydrocarbon composition controls the boiling point temperature. The
reactor is preferentially operated vapor continuous but may also be
operated liquid continuous. The pressure is preferentially higher
at the top of the reactor than at the bottom.
Adjusting the flow rates and the degree of vaporization controls
the pressure drop across the reactor. Multiple injection of olefin
is preferred. The type of packing also influences the pressure drop
due to the acid phase hold-up. The product mixture before
fractionation is the preferred circulating solvent. The acid
emulsion separates rapidly from the hydrocarbon liquid and is
normally-recycled with only a few minutes residence time in the
bottom phase separator. Because the products are in essence rapidly
extracted from the acid phase (emulsion), the reaction and/or
emulsion promoters used in conventional sulfuric acid alkylation
processes may be added without the usual concern for breaking the
emulsion. The process may be described as hydrocarbon continuous as
opposed to acid continuous.
Preferably, the disperser comprises a conventional liquid-liquid
coalescer of a type which is operative for coalescing vaporized
liquids. These are commonly known as "mist eliminators" or
"demisters", however, in the present invention the element
functions to disperse the fluid materials in the reactor for better
contact. A suitable disperser comprises a mesh such as a co-knit
wire and fiberglass mesh. For example, it has been found that a 90
needle tubular co-knit mesh of wire and multi-filament fiberglass
such as manufactured by Amistco Separation Products, Inc. of Alvin,
Tex., can be effectively utilized, however, it will be understood
that various other materials such as co-knit wire and multi
filament teflon (Dupont.TM.), steel wool, polypropylene, PVDF,
polyester or various other co-knit materials can also be
effectively utilized in the apparatus. Various wire screen type
packings may be employed where the screens are woven rather than
knitted. Other acceptable dispersers include perforated sheets and
expanded metals, open flow cross channel structures which are
co-woven with fiberglass or other materials such as polymers
co-knit with the wire mesh expanded or perforated sheets.
Additionally the multi-filament component may be catalytic. The
multi-filament catalytic material may be polymers, such as
sulfonated vinyl resin (e.g., Amberlyst) and catalytic metals such
as Ni, Pt, Co, Mo, Ag.
The disperser comprises at least 50 volume % open space up to about
97 volume % open space. Dispersers are position within the reaction
zone in the reactor. Thus, for example, the multi filament
component and the structural element, e.g., knit wire, should
comprise about 3 volume % to about 50 volume % of the total
disperser, the remainder being open space.
Suitable dispersers include structured catalytic distillation
packings which are intended to hold particulate catalysts, or
structured distillation packings composed of a catalytically active
material, such as that disclosed in U.S. Pat. No. 5,730,843 which
is incorporated herein in its entirety and which discloses
structures that have a rigid frame made of two substantially
vertical duplicate grids spaced apart and held rigid by a plurality
of substantially horizontal rigid members and a plurality of
substantially horizontal wire mesh tubes mounted to the grids to
form a plurality of fluid pathways among the tubes, said tubes
being empty or containing catalytic or non catalytic materials; and
structured packings which are catalytically inert which are
typically constructed of corrugated metal bent at various angles,
wire mesh which is crimped, or grids which are horizontally stacked
one on top of the other, such as disclosed in U.S. Pat. No.
6,000,685 which is incorporated herein in its entirety and which
discloses contact structures comprising a plurality of sheets of
wire mesh formed into vee shaped corrugations having flats between
the vees, said plurality of sheets being of substantially uniform
size having the peaks oriented in the same direction and
substantially in alignment, said sheets being separated by a
plurality of rigid members oriented normally to and said resting
upon said vees.
Other suitable dispersers include: (A) random or dumped
distillation packings which are: catalytically inert dumped
packings contain higher void fraction and maintain a relatively
large surface area, such as, Berl Saddles (Ceramic), Raschig Rings
(Ceramic), Raschig Rings (Steel), Pall rings (Metal), Pall rings
(Plastic, e.g. polypropylene) and the like and catalytically active
random packings which contain at least one catalytically active
ingredient, such as Ag, Rh, Pd, Ni, Cr, Cu, Zn, Pt, Tu, Ru, Co, Ti,
Au, Mo, V, and Fe as well as impregnated components such a
metal-chelate complexes, acids such as phosphoric acid, or bonded,
inorganic, powdered materials with catalytic activity; and (B)
monoliths which are catalytically inert or active which are
structures containing multiple, independent, vertical channels and
may be constructed of various materials such as plastic, ceramic,
or metals, in which the channels are typically square; however,
other geometries could be utilized, being used as such are coated
with catalytic materials.
The hydrocarbon feedstock undergoing alkylation by the method of
the present invention is provided to the reaction zone in a
continuous hydrocarbon phase containing effective amounts of
olefinic and isoparaffinic starting materials which are sufficient
for forming an alkylate product. The olefin:isoparaffin mole ratio
in the total reactor feed should range from about 1:1.5 to about
1:30, and preferably from about 1:5 to about 1:15. Lower
olefin:isoparaffin ratios may also be used.
The olefin component should preferably contain 2 to 16 carbon atoms
and the isoparaffin component should preferably contain 4 to 12
carbon atoms. Representative examples of suitable isoparaffins
include isobutane, isopentane, 3-methylhexane, 2-methylhexane,
2,3-dimethylbutane and 2,4-dimethylhexane. Representative examples
of suitable olefins include butene-2, isobutylene, butene-1,
propylene, pentenes, ethylene, hexene, octene, and heptene, merely
to name a few and as described above may be oligomers of these
olefins.
In the fluid process the system uses hydrofluoric or sulfuric acid
catalysts under relatively low temperature conditions. For example,
the sulfuric acid alkylation reaction is particularly sensitive to
temperature with low temperatures being favored in order to
minimize the side reaction of olefin polymerization. Petroleum
refinery technology favors alkylation over polymerization because
larger quantities of higher octane products can be produced per
available light chain olefins. Acid strength in these liquid acid
catalyzed alkylation processes is preferably maintained at 88 to
94% by weight using the continuous addition of fresh acid and the
continuous withdrawal of spent acid. The process may be carried out
in some embodiments using a solid phase alkylation catalyst. The
process may be carried out in some embodiments using a solid phase
alkylation catalyst, for example, solid phosphoric acid may be used
by supporting the catalysts within or on the packing material.
Preferably, the process of the present invention should incorporate
relative amounts of acid and hydrocarbon fed to the top of the
reactor in a volumetric ratio ranging from about 0.01:1 to about
2:1, and more preferably in a ratio ranging from about 0.05:1 to
about 0.5:1. In the most preferred embodiment of the present
invention, the ratio of acid to hydrocarbon should range from about
0.1:1 to about 0.3:1.
Additionally, the dispersion of the acid into the reaction zone
should occur while maintaining the reactor vessel at a temperature
ranging from about 0.degree. F. to about 200.degree. F., and more
preferably from about 35.degree. F. to about 130.degree. F.
Similarly, the pressure of the reactor vessel should be maintained
at a level ranging from about 0.5 ATM to about 50 ATM, and more
preferably from about 0.5 ATM to about 20 ATM. Most preferably, the
reactor temperature should be maintained within a range from about
40.degree. F. to about 110.degree. F. and the reactor pressure
should be maintained within a range from about 0.5 ATM to about 5
ATM.
In general, the particular operating conditions used in the process
of the present invention will depend to some degree upon the
specific alkylation reaction being performed. Process conditions
such as temperature, pressure and space velocity as well as the
molar ratio of the reactants will affect the characteristics of the
resulting alkylate product and may be adjusted in accordance with
parameters known to those skilled in the art.
An advantage of operating at the boiling point of the present
reaction system is that there is some evaporation which aids in
dissipating the heat of reaction and making the temperature of the
incoming materials closer to that of the materials leaving the
reactor as in an isothermal reaction.
Once the alkylation reaction has gone to completion, the reaction
mixture is transferred to a suitable separation vessel where the
hydrocarbon phase containing the alkylate product and any unreacted
reactants is separated from the acid. Since the typical density for
the hydrocarbon phase ranges from about 0.6 g/cc to about 0.8 g/cc
and since densities for the acid generally fall within the ranges
of about 0.9 g/cc to about 2.0 g/cc, the two phases are readily
separable by conventional gravity settlers. Suitable gravitational
separators include decanters. Hydrocyclones, which separate by
density difference, are also suitable.
One alkylation embodiment is shown in the FIGURE which is a
simplified schematic representation of the apparatus and flow of
the process. Such items as valves, reboilers, pumps, etc., have
been omitted.
The reactor 10 is shown containing a disperser mesh 40. The present
dispersers achieve radial dispersion of the fluid or fluidized
materials in the reactor. The feed to the reactor comprises an
olefin fed via line 12 such as n-butene and an isoparaffin (e.g.,
isobutane) fed via line 14 through line 52. Preferably a portion of
the olefin is fed along the reactor via lines 16a, 16b, and 16c. A
liquid acid catalyst such as H.sub.2SO.sub.4 is fed via line 56 and
make-up acid may be supplied through line 38. The hydrocarbon
reactants are fed to the reactor which is preferably a generally
cylindrical column via line 58 and through appropriate dispersing
means (not shown) into the disperser mesh 40, for example, a
co-knit wire and fiberglass mesh.
The hydrocarbon reactants and non reactive hydrocarbons (e.g.,
normal butane) are intimately contacted with the acid catalyst as
the alkylation proceeds. The reaction is exothermic. The pressure
as well as the quantities of reactants are adjusted to keep the
system components at the boiling point but partially in the liquid
phase as the system components pass down flow through the reactor
in mixed vapor\liquid phase and out through line 18 into decanter
30. Under these conditions some of the alkylation catalyst is in
the vapor phase. In the decanter the system components are
separated into an acid phase 46 containing the catalyst, a
hydrocarbon phase 42 containing the alkylate, unreacted olefin and
unreacted isoparaffin, and non reactive hydrocarbons and a vapor
phase 44 which may contain some of each of the components and any
lighter hydrocarbon components which are removed from the system
via line 50 for further handling as appropriate.
Most of the acid phase is recycled via line 24 and 56 into the
reactor. Make-up acid may be added via line 38 and build-up spent
acid removed via line 48.
The hydrocarbon liquid phase is removed via line 22 with a portion
recycled to the top of the reactor via line 28. The remainder of
hydrocarbon phase is fed to distillation column 20 via line 26
where it is fractionated. Normal butane, if present in the feed,
can be removed via line 36 and the alkylate product is removed via
line 34. The overheads 32 are primarily unreacted isoalkane which
is recycled via line 52 to the top of reactor 10.
Experimental Set Up for Alkylation of Isoparaffin+Olefin
For the following examples the laboratory reactor is 15 feet high
by 1.5 inches diameter. It is packed with varying amounts and types
of packing material. The H.sub.2SO.sub.4 inventory is about 1 liter
depending on the holdup of the packing used. The surge reservoir is
about 3 liters and passes all the acid plus liquid hydrocarbon out
the bottom to circulate a two-phase mixture with a single pump.
Feeds are introduced at the top of the reactor to flow down with
the recycle mixture. Vapor is produced by heat of reaction plus
ambient heat gains and helps force the liquids down through the
packing creating great turbulence and mixing. Most of the vapors
are condensed after the reactor outlet. Uncondensed vapor and
liquid hydrocarbon product passes through an acid de-entrainer then
through the backpressure regulator to the de-isobutanizer. Mass
flow meters are used for feed flows and a Doppler meter measures
the circulation rate. Liquid products from the de-isobutanizer are
weighed. However, the vent flow rate is estimated as being the
difference between the mass flow metered feed in and the weighed
liquid products out. GC analyzes all hydrocarbon products,
including the vent. Titration is used for spent acid assay.
Operation
In the following examples the experimental unit circulates
hydrocarbon and acid down flow at the boiling point of the
hydrocarbons present. Pressure and temperature readings are logged
electronically. The reactor outlet temperature and pressure are
used to calculate the amount of iC.sub.4 in the recycle hydrocarbon
using an iC.sub.4/Alkylate flash calculation.
A backpressure regulator that passes both product liquid and vapor
to the de-isobutanizer tower, maintains the pressure. A small
amount of N.sub.2 may be used primarily to keep acid from backing
up into the feed line. However, too much N.sub.2 will cause a
decrease in product quality by diluting reactive isoparaffin in the
vapor phase.
The circulation pump in the experimental setup circulates both the
acid emulsion layer and the liquid hydrocarbon layer.
Alternatively, these two phases may be pumped separately.
The acid inventory is maintained by momentarily diverting the
entire recycle through a measuring tube using a three-way valve.
The trapped material settles in seconds to form two layers. The
volume percent acid layer and hydrocarbon layer is then used in
conjunction with the Doppler meter reading to estimate the
volumetric circulation rates of both phases.
The DP (pressure higher at the top or reactor inlet) is maintained
between 0 and 3 psi by manipulating the circulation rates and the
heat balance around the unit. Different packing usually requires
different vapor and liquid flow rates to load to the same DP. Most
of the time, the ambient heat gains and the heat of reaction
provide adequate vapor (mostly iC.sub.4) loading.
Because of refrigeration constraints, about 1-3 lbs/hr of extra
liquid iC.sub.4 may be introduced with the feed to provide some
trim cooling. This excess iC.sub.4 is relatively small and does not
significantly affect the iC.sub.4/Olefin ratio since the
circulating hydrocarbon rates are typically on the order of 100-200
pounds per hour. It is the circulating hydrocarbon flow rate and
composition that dominates the iC.sub.4 ratios to everything
else.
TABLE-US-00001 TYPICAL OPERATING CONDITIONS FOR C4 ALKYLATION IN
THE EXAMPLES Feed olefin C4's Olefin in - lbs/hr 0.25-.50 Alky out
- lbs/hr 0.50-1.2 Rxn Temp out - F 50-60 Rxn Psig out 6-16 DP - Psi
0.5-3.0 Recycle rates: Acid phase-L/min 0.3-1 HC phase - L/min 1-3
Wt % iC4 in HC recycle 75-45 Wt % H2SO4 in Spent acid 83-89 Wt %
H2O in Spent acid 2-4 Fresh acid addition - lbs/gal alky 0.3-0.5
Packing Type 1 or 2 - see notes below Packing Hgt in feet 10-15
Pack density lbs/ft3 5-14 Notes: 1. Packing type 1 is .011 inch
diameter 304 ss wire coknitted with 400 denier multifilament
fiberglass thread every other stitch. 2. Packing type 2 is .011
inch diameter alloy 20 wire coknitted with 800 denier multifilament
poly propylene yarn every other stitch.
TABLE-US-00002 Example 1 Refinery C4 Olefins used as feedstocks To
the Lab Unit: Low iB 38% iB in total olefins methane 0.02 0.00
ethane 0.00 0.00 ethene 0.00 0.00 propane 0.77 0.41 propene 0.14
0.16 propyne 0.02 0.00 propadiene 0.01 0.02 iso-butane 23.91 47.50
iso-butene 0.90 15.90 1-butene 20.02 10.49 1,3-butadiene 0.02 0.19
n-butane 22.63 10.79 t-2-butene 18.05 7.93 2,2-dm propane 0.09 0.00
1-butyne 0.00 0.01 m-cyclopropane 0.03 0.03 c-2-butene 12.09 5.43
1,2-butadiene 0.00 0.01 3M-1-butene 0.26 0.04 iso-pentane 0.98 0.02
1-penetene 0.06 0.82 2M-1-butene 0.01 0.01 n-pentane 0.01 0.03
t-2-pentene 0.00 0.08 c-2-pentene 0.00 0.00 t-3-pentandiene 0.00
0.08 c-1,3-pentadiene 0.00 0.00 unknowns 0.01 0.08 100.00 100.00
Comparison of Refinery produced Alkylated with Lab Unit results
using similar low iB C4 feed Plant A Plant B Lab 1 Lab 2 iC5 6.27
2.70 2.51 2.78 2,3-dmb 4.05 2.84 2.80 3.02 C6 1.63 1.19 1.00 1.15
2,2,3-tmb 0.20 0.17 0.18 0.19 C7 7.17 5.55 4.35 4.35 TM C8 53.88
61.76 66.84 66.93 DM C8 12.27 12.47 12.69 12.44 TM C9 5.04 4.22
2.89 2.74 DM C9 0.57 1.01 0.29 0.18 TM C10 1.14 0.91 0.70 0.64 UNK
C10 0.51 0.54 0.29 0.29 TM C11 0.99 0.77 0.69 0.71 UNK C11 1.09
0.02 0.00 0.00 C12 4.37 1.71 4.72 4.60 C13 0.00 1.58 0.00 0.00 C14
0.03 1.57 0.05 0.00 C15 0.00 0.13 0.00 0.00 HV'S 0.05 0.04 0.00
0.00 UNK 0.74 0.83 0.00 0.00 sum 100.00 100.00 100.00 100.00 Avg MW
110.2 113.4 112.8 112.4 Bromine no. <1 <1 <1 <1 Total
Sulfur ppm <10 <10 <10 <10 TOTAL % TM 61.05 67.66 71.12
71.01 TM C8/DM C8 (ratio) 4.39 4.95 5.27 5.38 TM C9/DM C9 (ratio)
8.85 4.19 10.08 15.57 Typical vent analysis: wt % hydrogen 0.000
oxygen 0.124 nirogen 3.877 methane 0.019 carbon monoxide 0.000
carbon dioxide 0.000 ethane 0.000 ethene 0.000 ethyne 0.000 propane
1.066 propene 0.000 propadiene 0.000 iso-butane 81.233 iso-butene
0.021 1-butene 0.000 1,3-butadiene 0.031 n-butane 3.398 t-2-butene
0.000 m-cyclopropane 0.000 c-2-butene 0.000 iso-pentane 0.968
1-pentene 0.000 n-pentane 0.000 C5 + 0.391 Example 2 Effect of
Isobutylene (iB) on Alky Quality 100% iB 38% iB lab 1 low iB iC5
3.66 3.97 2.78 2,3-dmb 3.60 3.56 3.02 C6 1.42 0.52 1.15 2,2,3-tmb
0.40 0.23 0.19 C7 5.27 5.08 4.35 TM C8 50.79 56.95 66.93 DM C8
11.77 12.64 12.44 TM C9 6.07 4.22 2.74 DM C9 0.58 0.45 0.18 TM C10
2.06 1.33 0.64 UNK C10 1.14 0.67 0.29 TM C11 2.54 1.28 0.71 UNK C11
1.00 0.00 0.00 C12 8.30 8.99 4.60 C13 0.07 0.00 0.00 C14 0.28 0.14
0.00 C15 0.12 0.00 0.00 HV'S 0.38 0.00 0.00 UNK 0.54 0.00 0.00 sum
100.00 100.00 100.00 Avg MW 115.1 113.8 112.4 Bromine no. ~1 <1
<1 Total Sulfur ppm <10 <10 <10 TOTAL % TM 61.46 63.77
71.12 TM C8/DM C8 4.31 4.51 5.27 TM C9/DM C9 10.51 9.34 10.08
Example 3 Propylene + iC4 Alkylation Sample Point product propane
0.01 iso-butane 9.25 n-butane 0.32 iso-pentane 0.97 n-pentane 0.00
2,3-dm butane 2.07 2M-pentane 0.30 3M-pentane 0.14 n-hexane 0.00
2,4-dm pentane 15.59 2,2,3-tm butane 0.04 3,3-dm pentane 0.01
cyclohexane 0.00 2M-hexane 0.34 2,3-dm pentane 48.97 1,1-dm
cyclopentane 0.00 3M-hexane 0.35 2,2,4-tm pentane 3.42 n-heptane
0.00 2,5-dm hexane 0.37 2,4-dm hexane 0.56 2,3,4-tm pentane 1.52
2,3,3-tm pentane 1.21 2,3-dm hexane 0.64 2,2,5-tm hexane 0.68
2,3,4-tm hexane 0.13 2,2-dm heptane 0.01 2,4-dm heptane 0.03 2,6-dm
heptane 0.03 2,2,4-tm-heptane 1.83 3,3,5-tm-heptane 1.70
2,3,6-tm-heptane 1.16 2,3,5-tm-heptane 0.16 tm-heptane 1.00
2,2,6-trimethyloctane 2.32 C8s 0.20 C9s 0.20 C10s 0.98 C11s 1.62
C12s 1.73 C13s 0.09 C14s 0.05 C15s 0.01 unknowns 0.01 heavies 0.00
100.00 Example 4 Isobutane + pentene 1 alkylation product Wt % C5
5.03 2,3-dmb 0.74 C6 0.35 DM C7 1.14 C7 0.17 TM C8 22.26 DM C8 3.70
TM C9 52.40 DM C9 6.72 TM C10 1.51 UNK C10 0.56 TM C11 0.16 UNK C11
0.38 C12 3.68 C13 0.33 C14 0.11 C15 0.08 HV'S 0.03 UNK 0.63 100.00
Avg MW 120.2 expected MW 128 feed olefin #/hr 0.25 Alky product
#/hr 0.47 Example 5 Oligomerization product from C4 feedstock with
38% iB in total olefins. (This product was in turn used as the
olefin feed to the lab Alkylation unit) iso-butane 48.8 iso-butane
+ 1-butene 1.6 n-butane 11.2 t-2-butene 14.3 c-2-butene 6.5
iso-pentane 1.0 t-2-pentene 0.1 unknowns 1.5 2,4,4-tm-1-pentene 4.7
2,4,4-tm-2-pentene 1.3 other C8's 3.4 grouped C12's 4.4 grouped
C16's 1.2 100.00 Oligomerication effect on Alky products using C4
feed with iB = 38% of Olefins before after iC5 3.97 2.39 2,3-dmb
3.56 2.87 C6 0.52 1.17 2,2,3-tmb 0.23 0.20 C7 5.08 4.95 TM C8 56.95
58.34 DM C8 12.64 12.80 TM C9 4.22 4.15 DM C9 0.45 0.35 TM C10 1.33
1.29 UNK C10 0.67 0.57 TM C11 1.28 1.41 UNK C11 0.00 0.00 C12 8.99
9.41 C13 0.00 0.00 C14 0.14 0.11 C15 0.00 0.00 HV'S 0.00 0.00 UNK
0.00 0.00 sum 100.00 100.00 Avg MW 113.8 115.1
Bromine no. <1 <1 Total Sulfur ppm <10 <10 TOTAL % TM
63.77 65.19 TM C8/DM C8 4.51 4.56 TM C9/DM C9 9.34 11.75 Operating
conditions: Olefin in - lbs/hr .25 .25 Alky out - lbs/hr .53 .53
Rxn Temp out - F 52.0 52.2 Rxn Psig out 12.2 11.8 DP - Psi ~1 ~1
Recycle rates: Acid phase-L/min 1.0 1.0 HC phase - L/min 2.6 2.6 %
iC4 in HC recycle 69 67 Packing Type 2 2 Packing Hgt in feet 15 15
Pack density lbs/ft3 7 7 Example 6 Alkylate quality from Isobutene
+ Isobutane or Oligomers of iB + iC4. iB DIB TIB+ IC5 3.66 3.97
3.41 2,3-dmb 3.60 3.70 3.18 C6 1.42 1.36 1.53 2,2,3-tmb 0.40 0.38
0.27 C7 5.27 4.96 6.39 TM C8 50.79 47.93 38.35 DM C8 11.77 8.92
12.91 TM C9 6.07 6.60 10.31 DM C9 0.58 0.81 1.10 TM C10 2.06 3.09
3.29 UNK C10 1.14 1.18 1.35 TM C11 2.54 2.53 2.72 UNK C11 1.00 1.79
0.00 C12 8.30 10.51 14.97 C13 0.07 0.31 0.07 C14 0.28 1.47 0.14 C15
0.12 0.29 0.00 HV'S 0.38 0.19 0.00 UNK 0.54 0.01 0.00 Sum 100.00
100.00 100.00 Avg MW 115.1 117.0 118.1 Bromine no. ~1 ~1 ~1 Total
Sulfur ppm <10 <10 <10 TOTAL % TM 61.46 60.15 54.67 TM
C8/DM C8 4.31 5.37 2.97 TM C9/DM C9 10.51 8.15 9.37 Operating
conditions: Feed olefin iB DIB TIB+ Olefin in - lbs/hr 0.25 0.40
0.25 Alky out - lbs/hr 0.49 0.78 0.48 Rxn Temp out - F 52 51.6 51.7
Rxn psig out 13 13.5 5.7 DP - psi 2.5 1.1 ~1 Recycle rates: Acid
phase - L/min 0.8 0.5 1.0 HC phase - L/min 1.8 1.4 3.0 % iC4 in HC
recycle 73 76 45 Packing Type 1 1 2 Packing Hgt in feet 10 10 15
Pack density lbs/ft3 6 6 7 Example 7 Expacted vs. actual alkylation
product MW's and moles iC4 uptake with various olefins (e.g. in
theory 1 mole of C6 olefin should react with 1 mole of iC4 to form
a C10 alkylate; MW = 142) Results indicate depolymerication
generating more and lower MW olefins that combine with additional
iC4. Moles iC4 uptake per more Olefin fed Average product MW Olefin
Expected Actual Expected Actual Hexene-1 1.0 1.2 142 124 Octene-1
1.0 1.4 170 130 Di-isobutylene 1.0 1.8 170 117 Tri-isobutylene+ 1.0
2.6 226 118 Example 8 Isobutane + pentene 1 alkylation product Wt %
IC5 5.03 2,3-dmb 0.74 C6 0.35 DM C7 1.14 C7 0.17 TM C8 22.26 DM C8
3.70 TM C9 52.40 DM C9 6.72 TM C10 1.51 UNK C10 0.56 TM C11 0.16
UNK C11 0.38 C12 3.68 C13 0.33 C14 0.11 C15 0.08 HV'S 0.03 UNK 0.63
100.00 Avg MW 120.2 expected MW 128 feed olefin #/hr 0.25 Alky
product #/hr 0.47
* * * * *